The present invention relates to a thermoplastic resin composition excellent in antistatic property inclusive of its aging resistance and flame retardant property.
In the prior art, thermoplastic resins are provided with fairly satisfactory lasting and durable antistatic property by incorporation of, for example, a polyether diol amide or ester condensate as disclosed in Japanese Kokai Pat. Pub. Nos. 60-23435, 04-5691 and 03-258850 or a polyether-based copolymer derived from ethylene oxide, epichlorohydrin, etc. as disclosed in Japanese Kokai Pat. Pub. No. 63-314261.
It is also known that thermoplastic resins can be made antistatic by addition of surfactants, such as sodium alkanesulfonates, N,N-diethoxylated laurylamine, stearic acid monoglyceride, etc.
On the other hand, thermoplastic resins can be rendered flame resistant or flame retardant by incorporation of flame retardants.
Nowadays, attempts are being made to produce resins having combined flame retardant and antistatic properties.
A number of attempts has been made to incorporate both an antistatic agent of the polyether-based copolymer type mentioned above and a flame retardant in thermoplastic resins or incorporate both an antistatic agent of said surfactant type and said flame retardant in such resins. However, no satisfactory result has been obtained in either case. It is a commonly held belief in the art that resin compositions having satisfactory levels of flame retardancy and antistatic property, to say nothing of durable antistatic property, in good valance can never be obtained.
Thus, for example, when an antistatic agent, e.g. a polyether ester (amide) condensate or a polyether copolymer such as mentioned above, and a flame retardant are added to a resin, the resulting composition fails to show satisfactory flame retardancy or, in other words, to meet the requirements of the relevant UL (Underwriters' Laboratories) standard, since the antistatic agent itself contains a large proportion of ether oxygen and, hence, is very readily combustible even in the presence of a flame retardant.
When a flame retardant and a surfactant are used combinedly, a certain level of flame retardancy can be obtained. However, since the surfactant produces an antistatic effect as a result of its migration to the surface, said effect can hardly be maintained for a prolonged period of time. In many cases, the surfactant interacts with the flame retardant, resulting in failure to produce any significant effect.
Thus, as mentioned previously, it is common sense in the art that it is impossible to provide resin compositions having both the physical properties, i.e. flame retardancy and durable antistatic property, each at a satisfactory level.